Assay test system for regulating temperature

ABSTRACT

A device for evaluating at least one analyte in a test sample. The device comprises a cassette having a hollow test chamber, a test strip disposed within the test chamber for receiving the test sample, and a temperature control member. The cassette has at least one aperture extending from an exterior of the cassette to the hollow test chamber. The test strip includes a reagent adapted to react with the at least one analyte to produce a reaction indicative of the presence of the analyte. The temperature control member is adapted to extend through the at least one aperture in the cassette and into the test chamber for controlling the temperature of the test chamber.

FIELD OF THE INVENTION

The present invention relates generally to the field of qualitative andsemi-qualitative assays, and more particularly to a cassette forregulating the temperature for an assay.

BACKGROUND OF THE INVENTION

Immunochromatographic strip formats have become increasingly popular forqualitative and semi-quantitative assays which use visual detectionschemes. This type of assay involves the application of a liquid testsample suspected of containing an analyte to be detected to anapplication zone of an immunochromatographic test strip. The strip iscomprised of a matrix of absorbent material through which the test fluidand reagents for detecting the analyte can flow by capillarity from thestrip's application zone to a capture zone where a detectable signal, orthe absence thereof, reveals the presence of the analyte. Typically, thestrip will include means for immunospecifically binding the analyte tobe detected with its specific binding partner which bears the detectablelabel. In one such scheme, the strip contains an enzyme-labeled, mobilebinding partner for the analyte which is located in a zone downstreamfrom the sample application zone. If analyte is present in the testsample, it will combine with its labeled binding partner to form acomplex which will flow along the strip to a detection zone whichcontains a substrate for the enzyme label which is capable of providinga colored response in the presence of the enzyme. The strip may containa zone in which the analyte is immobilized, so that a labeled bindingpartner which does not combine with analyte, due to the absence ofanalyte in the sample, will be captured and thereby inhibited fromreaching the detection zone. There have been various modifications ofthis technique, all of which involve some competitive specific bindingsystem in which the presence or absence of analyte in the test sample isdetermined by the detection or lack thereof of labeled binding partnerin the detection zone.

An alternative to the above described immunometric assay which detectsthe free-labeled binding partner is the so-called sandwich format inwhich the capture zone contains immobilized antibodies against anepitope of the analyte which is different from the epitope to which thelabeled antibody is specific. In this format, the analyte is sandwichedbetween the immobilized and labeled specific binding partners, and it istherefore an immunometric assay which detects the bound, labeledspecific binding partner.

Not all of the schemes for immunochromatography rely on anenzyme-labeled binding partner/enzyme substrate for providing the signalfor detection of the analyte. For example, U.S. Pat. No. 4,806,311discloses a multizone test device for the specific binding assaydetermination of an analyte and an immobilized binding partner therefortogether with a capture zone for receiving labeled reagent whichmigrates thereto from the reagent zone. The capture zone contains animmobilized form of a binding substance for the labeled reagent. Thelabeled reagent bears a chemical group having a detectable physicalproperty, so that it does not require a chemical reaction with anothersubstance in order to be detected. Exemplary of such groups are speciesof fluorescers, phosphorescent molecules, radioisotopes andelectroactive moieties.

U.S. Pat. No. 4,703,017 describes the use of visible particulate labelsfor the receptor. Various particulate labels such as gold sol particlesand visible dye containing liposomes are mentioned. PCT PatentApplication Publication No. WO 96/34271 discloses a device fordetermining a target analyte and creatinine in a fluid test sample. Thedevice has an assay strip for the detection of creatinine and a secondassay strip for the detection of the target analyte. The creatinineconcentration can be determined colorimetrically or by the specificcapture of labeled creatinine binding partners. The concentration of thetarget analyte is corrected based on the sample's creatinineconcentration which correction can either be done manually or by meansof a properly programmed reflectance analyzer.

Immunochromatographic strip formats provide a viable system for thedetermination of various analytes (whether they be antigens orantibodies) but suffer from the limitation that they yield results whichare at best semi-quantitative when, for some analytes, more precise,quantitative results are required. The strip can be prepared from anymatrix material through which the test fluid carrying the analyte andlabeled binder-analyte contained therein can flow by capillarity; thematrix can be of a material which is capable of supporting non-bibulouslateral flow, described in U.S. Pat. No. 4,943,522 as liquid flow inwhich all of the dissolved or dispersed components of the liquid arecarried through the matrix at substantially equal rates and withrelatively unimpaired flow as contrasted to preferential retention ofone or more components as would be the case if the matrix material werecapable of absorbing or imbibing one or more of the components. Anexample of such matrix material is the high density or ultra highmolecular weight polyethylene sheet material from Porex Technologies ofFairburn, Ga. Equally suitable for use as the matrix from which thechromatographic strip can be fabricated are bibulous materials such aspaper, nitrocellulose, and nylon.

One variable which needs to be controlled in analyses usingimmunochromatographic strips is temperature control. Temperature is animportant variable because all immunochemical reactions arecharacterized by two temperature-dependent opposite reactions at thesame time. These are the formation of an immune complex from an antigenand its antibody and the appearance of free antigen and antibody bydissociation of the immuno complex. Increasing the temperature increasesthe rate of reaction, and because immunochromatographic strip formatsare usually measured under nonequilibrium conditions due to the shortassay times involved, temperature control, both within and betweenlaboratories, is critical for insuring consistent reaction rates therebyproviding more reproducible assay quantitation. Currently, temperatureis not controlled. Typically immunochromatographic strips are run atambient temperatures which can range from 20-30° Centigrade. Becausereaction rates approximately double for every 10 degree centigradeincrease in temperature, it is apparent that controlling temperatureallows for control of the immunochemical reaction thereby leading tomore reproducible results.

Devices for controlling the temperature of an assay include a disposabletest cassette having a thermally conductive member, such as an aluminumbar, disposed within the cassette. In such a device, the thermallyconductive bar is in thermal communication with the test strip forregulating the temperature of the assay. The thermally conductive baraccelerates the warning of the assay during an incubation period. Afterthe assay is completed, the cassette including the thermally conductivemember is discarded. These devices have achieved good results incontrolling the temperature of an assay. However, one drawbackassociated with such a device is that the thermally conductive member isdiscarded along with the disposable test cassette having the thermallyconductive member disposed therein. Therefore, the costs associated withproviding the thermally conductive member are incurred with each use ofthe disposable test cassette having a thermally conductive memberdisposed therein. Accordingly, there is a need for a low-cost, easilymanufacturable test cassette for controlling the temperature of anassay.

SUMMARY OF THE INVENTION

A device for evaluating at least one analyte in a test sample comprisesa cassette having a hollow test chamber, a test strip disposed withinthe test chamber for receiving the test sample, and temperature controlmember. The cassette has at least one aperture extending from anexterior of the cassette to the hollow test chamber. The test stripincludes a reagent adapted to react with the analyte to produce areaction indicative of the presence of the analyte. The temperaturecontrol member is adapted to extend through the aperture in the cassetteand into the test chamber for controlling the temperature of the testchamber.

The above summary of the present invention is not intended to representeach embodiment, or every aspect, of the present invention. Additionalfeatures and benefits of the present invention will become apparent fromthe detailed description, figures, and claims set forth below.

BRIEF DESCRIPTION OF THE FIGURES

Other objects and advantages of the invention will become apparent uponreading the following detailed description in conjunction with thedrawings in which:

FIG. 1 is a perspective view of a top and a bottom portion of cassetteaccording to one embodiment of the present invention;

FIG. 2 is a perspective view of a fixture plate having fins according toone embodiment of the present invention;

FIG. 3 is a perspective view of a bottom portion of a cassette upon afixture plate having fins according to one embodiment of the presentinvention;

FIG. 4 is a perspective view of a temperature control mechanismaccording to one embodiment of the present invention;

FIG. 5 is a perspective view of a cassette bottom and a heatingmechanism according to an alternative embodiment of the presentinvention;

FIG. 6 is a perspective view of a cassette bottom upon the heatingmechanism shown in FIG. 5;

FIG. 7 is a perspective view of a cassette bottom inserted into aheating mechanism according to another alternative embodiment of thepresent invention; and

FIGS. 8 and 9 are perspective views of opposite ends of the cassettebottom and corresponding hot air blowers according to the embodiment ofthe present invention shown in FIG. 7.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

As discussed in the background section, devices for controlling thetemperature of an assay include a disposable test cassette including athermally conductive member, such as an aluminum bar, disposed withinthe cassette. The thermally conductive member facilitates thetemperature control of the assay. However, a drawback associated withsuch a device is that the thermally conductive member is discarded alongwith the disposable test cassette having the thermally conductive memberdisposed therein.

The present invention provides a low-cost, easily manufacturable testcassette which allows a heating element to protrude into a test chamberof the cassette to control the temperature of an assay. The presentinvention eliminates the need for a separate temperature control member,such as the above-mentioned aluminum bar, to be disposed within the testcassette and is discarded with the test cassette after the assay. Asmentioned above, more accurate results can be obtained from the assaywhen the temperature of the assay is controlled.

Referring initially to FIG. 1, an assay test cassette 10 according toone embodiment of the present invention is shown. The test cassette 10includes a cassette top 12 and a cassette bottom 14 that are designed tomate with one another after a test strip (not shown), such as aimmunochromatographic test strip, has been placed into a test stripreceiving well 16 of the cassette bottom 14.

The cassette top 10 has an application port 18 through which the liquidtest sample is applied to the test strip and a viewing port 20 throughwhich the detection zone of the test strip can be viewed. The cassettemay optionally include slits (not shown) for venting purposes. Thecassette top 12 and bottom 14 are fabricated to form a hollow testchamber when mated. Before mating, a test strip is placed in the teststrip receiving well 16. The cassette 10 is designed so that theapplication region of the test strip (which may be the first regioncontaining the labeled specific binding agent or a separate region ofthe strip) is aligned with the sample application port 18 and thedetection region of the strip is aligned with the viewing port 20 whenthe top 12 and bottom 14 of the cassette are mated.

The cassette bottom 14 includes a pair of rectangular-shaped aperturesor slots 22 through which temperature controlling elements protrude intothe hollow test chamber of the cassette 10, when the cassette top 12 andbottom 14 are mated, for regulating the temperate of an assay. Thecassette bottom 14 can be equipped with a series of sockets 23 whichlock up with pins (not shown) in the cassette top 12 when the cassettetop 12 and bottom 14 are mated, to hold the top 12 and bottom 14 snuglytogether. The cassette bottom optionally includes a depression 24 tohold a desiccant.

Various immunochromatographic strip formats are suitable for use in thepresent invention. The strip typically has a first region (e.g., areagent pad) that is made of an absorbent material such as paper or amembrane that has been impregnated with a reagent associated with aparticular test to be performed. In conventional immunochromatographicdevices, the strip is then placed into the well 16 of the cassettebottom 14 so that the reagent pad is located under the sampleapplication port 18. Alternatively, the strip can have an applicationzone that is free of the reagent with the reagent region beingdownstream and in liquid communication therewith. Such a test strip isdisclosed in U.S. Pat. No. 4,446,232.

Referring to FIG. 2, a fixture plate 26 having integral fins 28 is shownfor providing temperature control to the test cassette 10 during anassay. The fixture plate 26 and fins 28 are fabricated such that thefins 28 constitute an integral part of the fixture plate 26. Byintegrally manufacturing the fixture plate 26 and fins 28, heat lossfrom the interfaces between the plate 26 and the fins 28 is mitigated.Put another way, the overall thermal conductivity of the fixture plateand fins would be reduced at the interface between the fins and fixtureplate if the fins were connected to the fixture plate with, for example,screws, instead of being integrally formed. The fixture plate 26 andfins 28 can be made out of any thermally conductive material which ismore thermally conductive than the cassette 10. (The cassette 10 is madeof plastic according to one embodiment of the present invention.)Thermally conductive materials for the plate 26 and fins 28 includecopper, gold, silver, aluminum, and other alloys with superior thermalproperties. In one embodiment of the present invention, the fixtureplate 26 and fins 28 are made out of aluminum. Aluminum is an excellentthermal conductor and is relatively low in cost in comparison to gold,silver, and copper.

Referring to FIG. 3, the cassette bottom 14 is shown laid upon thefixture plate 26 such that the fins 28 protrude through the slots 22disposed within the cassette bottom 14. When the cassette top 12 andbottom 14 are mated, the fins 28 extend up into the hollow test chamberof the cassette 10 to provide temperature control to the test chamberwhich contains the immunochromatographic test strip at the time of anassay.

Referring to FIG. 4, a temperature control mechanism 30 is shown. Thetemperature control mechanism 30 includes a cassette carrier 32, afixture carrier or heating device 34, and a circuit box 36. The cassettecarrier 32 is hingedly connected to the heating device 34 allowing acassette 10 placed within the cassette carrier 32 to be rotated downwardthus bringing the cassette bottom 14 into contact with the fixture plate26 which is disposed on the heating device 34. When the assay isconducted, a cassette 10 having a test strip disposed therein isinserted into the cassette carrier 32 through an opening 38 of thecassette carrier 32. After the cassette 10 is inserted into the carrier32, a door 40 of the cassette carrier 32 is closed to retain the heatgenerated within the enclosed space of the cassette carrier 32. Thecassette carrier 32 is then rotated downward.

The fixture plate 26 having integral fins 28 is thermally coupled to theheating device 34. Thus, the fixture plate 26 and the fins 28 are heatedby the heating device 34 by way of conduction. The heating device 34comprises a thermoelectric device such as, for example, a Peltier Effectthermoelectric device. The circuit box 36 contains the necessaryelectronics to provide power to and to control the electric heatingelement of the heating device 34 and optionally includes one or morelight emitting diodes 42 (“LEDs”) which provide a visual indication ofthe operational status of the mechanism 30.

When the cassette carrier is closed (e.g., downwardly rotated), thecassette bottom 14 is brought into contact with the fixture plate 26causing the fins 28 to protrude through the slots into the hollow testchamber. The fins 28, in turn, heat the test chamber thus regulating thetemperature of the reaction. Tension coil springs (not shown) betweenthe cassette carrier 32 and the fixture carrier 34 maintain contactbetween the cassette bottom 14 and the fixture plate 26.

In operation, a test strip is placed in the well 16 of the cassettebottom 14 which is then mated with the cassette top 12. A fluid testsample (e.g., urine) is applied to the first region of the test strip oroptional sample application pad. The fluid test sample flows through thefirst zone of the strip the fluid test sample and contacts the labeledantibodies which flow along with the fluid test sample towards thedetection zone. At the detection zone the labeled antibodies arecaptured either by interaction with immobilized analyte or interactionbetween analyte in the fluid test sample. Regardless of how the labeledantibodies are captured in the detection zone there will be a detectableresponse (absence of signal in the first case) which can be read by aproperly programmed reflectance spectrometer. In various assays, thepresence and/or the concentration of the analyte in the test sample isdetermined.

Many clinically significant target analytes are present in urine and aredeterminable by means of the type immunochromatographic stripscontemplated herein. Among these analytes are deoxypyridinoline, humanserum albumin and drugs of abuse such as amphetamines, barbiturates andcocaine. While the means for detecting the signal from the developedstrip of the device of the present invention will depend on thedetectable label attached to the labeled binding partner, the use of areflectance spectrometer is typical when the label's detectable physicalproperty is the reflectance of light at a predetermined wavelength.According to one embodiment of the present invention, there is provideda reflectance meter with means for moving the cassette containing thestrip or the meter's detector element relative to each other such as byuse of a specimen table for the strip which can be moved laterally underthe readhead of the detector. As previously discussed, maintenance ofcareful temperature control increases the accuracy of the assay.

While the depicted embodiments of the fixture plate 26 and the cassettebottom 14 show two pairs of two fins 28, corresponding to two slots,respectively, various other configurations are available in alternativeembodiments of the present invention. For example, the cassette bottom14 may contain four narrow slots corresponding to each of the fins.Alternatively, the fixture plate 26 may contain a plurality ofcylindrical shaped fins (e.g., rods), which protrude through circularholes in the cassette bottom 14 to provide temperature control on thetemperate in the hollowing

The cassette 10 is intended to be a disposable testing device. Having adisposable cassette 10 prevents or reduces the risk of contamination ofthe test area and the test sample. As discussed above, the cassette top12 and bottom 14 arc made of plastic. The cassette top 12 and bottom 14can be inexpensively manufactured by injection molding the top 12 andbottom 14 out of plastic including high impact polystyrene, ABS, orstyrene according to alternative embodiments of the present invention.According to one embodiment of the present invention, the cassettebottom 14 includes a wall (not shown) made of a thin plastic material toprevent physical contact between the test sample and the fins 28. Insuch an embodiment, the thin wall prevents or reduces the risk ofcross-contamination of subsequent test samples.

Referring now to FIGS. 5 and 6, an alternative embodiment of a cassettebottom 60 and heating mechanism 62 is shown. The heating mechanism 62includes a heater carrier 64 and resistive heating elements 66. Thecassette bottom 60 is designed to mate with a cassette top similar tothat shown FIG. 1. The cassette bottom illustrated in FIGS. 5 and 6includes rectangular shaped apertures 68 for receiving the resistiveheating elements 66. The resistive heating elements 66 protrude throughthe apertures 68 and into the hollow test chamber of the cassette whenthe cassette top (shown in FIG. 1) and the cassette bottom are mated.The cassette bottom 60 depicted in FIGS. 5 and 6 is similar to thatshown in FIG. 14, except that the rectangular shaped apertures 68 may besized differently than shown in FIGS. 1-4 depending on the physical sizeof the resistive heater elements.

When an assay is conducted, the heating mechanism 62 provides theadvantage of quick temperature control as the resistive heating elements66 rapidly heat up and, in turn, are able to quickly bring the hollowtest chamber of the cassette to the desired temperature. Further, lesstime is required to bring the test chamber to the desired temperaturebecause the heat source (i.e., the resistive heating elements 66) arebrought into very close proximity to the test strip.

According to one embodiment of the present invention, a device such asthe temperature control mechanism 30 illustrated in FIG. 4 may be usedwith the heating mechanism 62 illustrated in FIG. 5. The heatingmechanism 62 replaces the fixture plate 26 having integral fins 28. Thetemperate control mechanism operates in a manner similar to thatdescribed in connection with FIG. 4. The temperature control mechanismcontains circuitry designed to regulate the temperature inside thecassette by controlling the amount of current that passes through theresistive heating elements. According to an alternative embodiment, theheating mechanism 62 includes covers (not shown) disposed over theresistive heating elements 66 to prevent the resistive heating elements66 from contacting the test strip during the assay.

Referring now to FIGS. 7, 8, and 9, another alternative embodiment of acassette bottom 80 and a heating mechanism 82 is shown. The cassettebottom 80 is shown inserted into the heating mechanism 82. The cassettebottom 80 is designed to mate with a cassette top similar to that shownin FIG. 1. The heating mechanism 82 includes a cassette carrier 84 andhot air blowers 86 disposed towards opposite ends 88, 90 of the cassettebottom 80. As shown best in FIGS. 8 and 9, each end 88, 90 of thecassette bottom 80 contains hot air inlet apertures 92 which correspondto outlets 94 of the hot air blowers 86. Each of the hot air blowers 86includes a fan (not shown) which forces air over resistive heatingelements (not shown) to produce a flow of hot air that exits the hot airblowers 86 through the outlet apertures 94.

The amount of heating provided by each of the hot air blowers 86 canvary according to the amount of current supplied to the resistiveheating elements and the speed and size of the fan. Depending on thequantity of hot air produced by the hot air blowers 86, the heatingmechanism 82 can quickly heat the air in the test chamber of the testcassette to the desired temperature. The heating mechanism 82 includesan electric circuit (not shown) that is designed to control the requiredtemperature inside the cassette 80 by controlling the amount of currentsupplied to the resistive heating elements and the speed of the fan.

In conducting an assay, the test sample is applied to a test stripdisposed in a test cassette via the cassette application port. The testcassette is inserted into the heating mechanism 82 and the hot airblowers 86 are turned on. According to one embodiment of the heatingmechanism 82, the cassette carrier 84 contains a switch (not shown) sothat when the test cassette is inserted into the cassette carrier 84,the hot air blowers are automatically turned on. Hot air is blown intothe test chamber of the test cassette to raise the temperate of the testcassette to the desired level and then to maintain the test chamber atthat temperature. According to an alternative embodiment, the testcassette bottom 80 contains appropriate baffle plates and channels toavoid direct flow of the heated air over the test strip so thatevaporation of the test fluid is minimized. Additionally, according toone embodiment of the present invention, the cassette bottom includesone or more apertures allowing air to vent from the cassette bottom 80while the test chamber is being filled with hot air from the hot airblowers 86.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and herein described in detail. It should beunderstood, however, that it is not intended to limit the invention tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

1. A device for evaluating at least one analyte in a test sample, thedevice comprising: a disposable cassette having a hollow test chamberand at least one aperture extending from an exterior of the cassette tothe hollow test chamber; a test strip disposed within the test chamberfor receiving the test sample, the test strip including a reagent forreacting with the at least one analyte to produce a reaction indicativeof the presence of the analyte; and a temperature control membercomprising at least one fin positioned adjacent to, but not in directcontact with, said test strip and extending through the at least oneaperture in the cassette and into the test chamber for controlling thetemperature of the test chamber, and a thermoelectric temperaturecontrol unit in thermal communication with the at least one fin forcontrolling the temperature of the test chamber.
 2. The device of claim1 wherein the test strip comprises an immunochromatographic test strip.3. The device of claim 1 wherein the test strip is made out of abibulous material.
 4. The device of claim 1 wherein the cassette top andthe cassette bottom are made of plastic.
 5. The device of claim 1wherein the at least one fin comprises a plurality of fins, and whereinthe at least one aperture of the cassette comprises a plurality ofapertures, each of the plurality of apertures for receiving one or moreof the plurality of fins, one or more of the plurality of fins extendingthrough each of the plurality of apertures into the test chamber.
 6. Thedevice of claim 5 wherein the temperature control member furthercomprises a fixture plate attached to the plurality of fins, and whereinthe fixture plate and the plurality of fins are integrally formed. 7.The device of claim 6 wherein the fixture plate and the plurality offins are made out of a thermally conductive material.
 8. The device ofclaim 7 wherein the thermally conductive material is aluminum.
 9. Thedevice of claim 1 in combination with a spectrometer for reading thereaction indicative of the presence of the analyte.
 10. An apparatus forcontrolling the temperature of an assay test strip, the apparatuscomprising: a cassette carrier for receiving a disposable test cassettehaving at least one aperture; a thermally conductive member extendingthrough the at least one aperture of a test cassette received by thecassette carrier and positioned adjacent to, but not in direct contactwith, said test strip; and a temperature control unit in thermalcommunication with the thermally conductive member for controlling thetemperature of said cassette carrier.
 11. The apparatus of claim 10wherein the thermally conductive member is made of aluminum.
 12. Theapparatus of claim 10 wherein the thermally conductive member comprisesat least one fin fixedly attached to a fixture plate.
 13. The apparatusof claim 12 wherein the fixture plate and at least one fin areintegrally formed.
 14. The apparatus of claim 12 wherein the at leastone fin comprises two or more fins.
 15. The apparatus of claim 12wherein the material is a thermally conductive material.
 16. Theapparatus of claim 12 wherein the temperature control unit comprises athermoelectric device.
 17. The apparatus of claim 16 wherein thethermoelectric device is a Peltier Effect thermoelectric device.
 18. Amethod for evaluating at least one analyte in a test sample, the methodcomprising: providing a disposable test cassette having at least oneaperture; disposing a test strip within a test chamber of the testcassette, the test strip including a reagent for reacting with the atleast one analyte to produce a reaction indicative of the presence ofthe analyte; applying the test sample to the test strip; controlling thetemperature of the test chamber with a temperature control member inthermal communication with a thermoelectric temperature control unitextending through the at least one aperture formed in the test cassette,said temperature control member comprising at least one fin positionedadjacent to, but not in direct contact with, said test strip; andevaluating said analyte in said test sample by reading said reactionindicative of said analyte.
 19. The method of claim 18 furthercomprising detecting any change in the test strip.
 20. The method ofclaim 18 wherein the test strip comprises an immunochromatographic teststrip.
 21. The method of claim 18 further comprising forming the testcassette from a cassette top and a cassette bottom.
 22. The method ofclaim 18 wherein the temperature control member includes a fixture plateattached to the at least one fin, and wherein the fixture plate and theat least one fin are integrally formed.
 23. The method of claim 22wherein the fixture plate and the at least one fin are made out of athermally conductive material.
 24. A device for evaluating at least oneanalyte is a test sample, the device comprising: a disposable cassettehaving a hollow test chamber and at least one aperture extending from anexterior of the cassettes to the hollow test chamber; a test stripdisposed within the test chamber for receiving the test sample, the teststrip including a reagent for reacting with the at least one analyte toproduce a reaction indicative of the presence of the analyte; and atemperature control member comprising at least one resistive heatingelement, said temperature control member controlling the temperature insaid cassette by the current supplied to said at least one resistiveheating element.
 25. The device of claim 24 wherein the at least oneresistive heating element comprises a plurality of resistive heatingelements, and wherein the at least one aperture of the cassettecomprises a plurality of apertures, each of the plurality of aperturesreceiving one or more of the plurality of resistive heating elements,one or more of the plurality of resistive heating elements extendingthrough each of the plurality of apertures into the test chamber. 26.The device of claim 24 further comprising a circuit for controlling theamount of current supplied to the at least one resistive heatingelement.
 27. A method for evaluating at least one analyte in a testsample, the method comprising: providing a disposable test cassettehaving at least one aperture; disposing a test strip within a testchamber of the test cassette, the test strip including a reagent forreacting with the at least one analyte to produce a reaction indicativeof the presence of the analyte: applying the test sample to the teststrip; controlling the temperature of the test chamber with atemperature control member extending through the at least apertureformed in the test cassette, said temperature control member includingat least one resistive heating element, the temperature of said at leastone resistive heating element controlled by current supplied to said atleast one resistive heating element; and evaluating said analyte in thetest sample by reading said reaction indicative of said sample.
 28. Themethod of claim 27 wherein controlling further comprises controlling theamount of electrical current that passes through the at least oneresistive heating element.